It is known in the prior art to construct cushions or mattresses with layers of a resilient foam rubber or man-made polymeric material. For example, U.S. Pat. No. 3,118,153 to Hood discloses the use of a laminated foam construction with the inner and outer layers of different foam densities to help the cushion conform to and retain the shape of its covering without a special molding process. In U.S. Pat. No. 2,878,153 to Hacklander the use of multiple layers of foam is taught with the flow tendencies controlled by means of applying compression and tension to selected layers. Other patents, such as Shecter, U.S. Pat. No. 3,047,888, disclose laminar construction of cushions using various materials to control the firmness of the cushion.
A desirable characteristic of cushion is an initial softness upon depression followed by subsequent firmness on further depression. However, to the knowledge of the inventors there has been no attempt to engineer a cushion or mattress construction that achieves such a characteristic in an all foam cushion by selectively varying the relative thickness and firmness of the layers. A mattress or cushion having a compression modulus of at least 3 and in the range of 3-8 will exhibit comfort, but excellent support. The "compression modulus" as used herein is a measure of the aforesaid initial softness and subsequent firmness characteristic, and is defined by the ratio of the load weight necessary to compress a foam sample 65 percent of its thickness compared with the load weight necessary to compress the same foam sample 25 percent of its thickness.
In addition, to the knowledge of the inventors, there has been no attempt to engineer a laminated mattress construction that includes horizontally juxtaposed, multiple sections of varying firmness to provide one mattress that is equally comfortable to two people.